1. Field of the Invention
The present invention relates to a paper mask unit for use in setting a paper mask in an exposure station of a photographic printer.
2. Related Art
Conventionally, a long strip of photographic paper, which is wound in a roll, is used in a photographic printer, in order to make photographic prints efficiently. When the photographic paper is initially transported to the exposure station, the leading end of the photographic paper roll may be curled as it enters into an opening of the paper mask and thus jam against a margin of the paper mask opening.
For this reason, it has been suggested to insert a shielding plate for closing the mask opening during paper feeding, for example, in Japanese Laid-open Utility Model Application No. 63-43138. It has also been suggested to retract the photographic paper upward from a paper mask guide path in cooperation with insertion of a paper mask plate, when the paper mask plate is set in the exposure station (Japanese Laid-open Utility Model Application No. 62-176842).
However, a complicated mechanism is required for retracting the photographic paper upward in cooperation with insertion of the paper mask plate. Moreover, this solution does not take into account initial guiding of the photographic paper and, therefore, it is not well suited for automatic paper loading. In a case where the shielding plate is inserted during paper loading, it is necessary to manually insert and then remove the shielding plate every time a new strip of photographic paper is to be loaded. This procedure can be very cumbersome.
It is also known to print information about a picture frame along with the image thereof by illuminating a lithographic film with the information recorded thereon. The lithographic film is put on a letter printing aperture formed in the paper mask beside the picture image print frame. For this purpose, an additional lamp housing for illuminating the lithographic film is provided in the conventional paper mask unit.
When the size of the photographic paper is to be changed, the size of the paper mask must also be changed. In conventional paper masks, the position of the letter printing aperture varies depending on the mask size. Therefore, it is also necessary to change the position of the lamp housing in accordance with the mask size or the position of the letter printing aperture. As a result, the construction of the conventional paper mask unit is complicated.